General impact assessment methods

To ensure a uniform and transparent basis for the EIA, a general impact assessment methodology for the assessment of predictable impacts has been prepared together with a list of terminology.

The overall goal of the assessment is to describe the Severity of Impact caused by the project. The assessment comprises two steps; where the first step is an analysis of the magnitude of the pressure and an analysis of the sensitivity of the environmental fac-tor. Combining the two analyses leads to the Degree of Impact. In the second step;

the results from the Degree of Impact is combined with the importance leading to the Severity of Impact.

In some cases it is necessary to consider the risk of a certain impact occurring. In these cases, the Severity of Impact is considered against the Likelihood of the occur-rence, giving the Degree of Risk.

As far as possible the impacts are assessed quantitatively, accompanied by a qualita-tive argument. The assessment steps are shown in figure 4.1.

Figure 4.1 Drawing of the overall assessment approach.

The assessment of migratory birds bases on literature studies.

HR3-TR-042 v7 53 / 125 4.1.1.1. Magnitude of Pressure

There are several crucial steps in the outlined assessment procedure shown in figure 2.1. The foremost are the determination of the Magnitude of Pressure and the Sensi-tivity. The content of the Magnitude of Pressure is made up of;

 intensity (i.e., level of collision risk and barrier effect)

 duration (i.e., construction activities vs. permanent structures)

 range (i.e., spatial extent of a wind farm; number of turbines)

The intensity evaluates the force of the pressure and should as far as possible estimat-ed quantitatively.

The duration determines the time span of the pressure. Some pressures (like foot-prints) are permanent and do not have a finite duration. Some pressures occur in events of different duration.

The range of the pressure defines the spatial extent. Outside of the range, the pres-sure is regarded as non-existing or negligible.

Distinctions are made between direct and indirect pressures where direct pressures are those imposed directly by the Project activities on the environmental factors while the indirect pressures are the consequences of those impacts on other environmental fac-tors and thus express the interactions between the environmental facfac-tors.

The Magnitude of Pressure is described by pressure indicators. The indicators are based on the modes of action on the environmental factor in order to achieve most optimal descriptions of pressure for the individual factors; e.g. mm deposited sediment within a certain period.

As far as possible the Magnitude of Pressure is worked out quantitatively. The method of quantification depends on the specific pressure (spill from dredging, noise, vibration, etc.) and on the environmental factor to be assessed (calling for different aggregations of intensity, duration and range).

HR3-TR-042 v7 54 / 125 Table 4.1 Aggregates included in the Magnitude of Pressure.

Magnitude of Pressure

Intensity Duration Range

Very High Recovery takes longer than 10 years or is permanent

International

High Recovered within 10 years after end of construction

National

Medium Recovered within 5 years after end of construction

Regional

Low Recovered within 2 years after end of construction

Local

4.1.1.2. Sensitivity

The optimal way to describe the sensitivity to a certain pressure varies between the environmental factors. To assess the sensitivity more issues may be taken into consid-eration such as the intolerance to the pressure and the capability to recover after im-pairment or a temporary loss. In most cases the sensibility of a certain environmental factor will be collected from the literature and is very often given as a threshold value.

To assess the sensitivity of migratory birds for the two impacts “collision risk” and

“barrier effect”, many issues have be taken into consideration; such as flight altitude, flight agility, migration density etc.. The sensitivity to the certain pressures was taken from the current literature. The sensitivity to both pressures are discussed species-specifically (where possible) or for each species group.

4.1.1.3. Degree of Impact

In order to determine the Degree of Impact; the Magnitude of Pressure and Sensitivity are combined in a matrix, see Table 4.2. The Degree of Impact is the pure description of an impact to a given environmental factor without putting it into a broader perspec-tive (the latter is done by including the Importance in the evaluation, see below).

Table 4.2 The matrix used for the assessment of the Degree of Impact.

Sensitivity

Very high High Medium Low

Magnitude of pressure Very high Very High Very High High High

High Very High High High Medium

Medium High High Medium Low

Low Medium Medium Low Low

HR3-TR-042 v7 55 / 125 4.1.1.4. Importance

The importance of the environmental factor is assessed for each environmental sub-factor. Some sub-factors are assessed as a whole, but in most cases, the importance assessment is broken down into components and/or sub-components in order to con-duct a fulfilling environmental impact assessment.

Considerations about standing stock sizes and spatial distribution are important for some sub-factors, such as bird populations, and are in these cases incorporated into the assessment. The assessment is based on importance criteria defined by the func-tional value of the environmental sub-factor and the legal status given by EU direc-tives, national laws, etc.

The importance criteria are graded into four tiers, see Table 4.3. In a few cases, such as climate, grading does not make sense. As far as possible the spatial distribution of the importance classes are shown on maps.

Table 4.3 The definition of Importance to an environmental factor.

Importance level

Description

Very high Components protected by international legislation/conventions (Annex I, II and IV of the Habitats Directive, Annex I of the Birds Directive), or of international ecological importance. Com-ponents of critical importance for wider ecosystem functions.

High Components protected by national or local legislation, or adapted on national “Red Lists”. Components of importance for far-reaching ecosystem functions.

Medium Components with specific value for the region, and of im-portance for local ecosystem functions

Low Other components of no special value, or of negative value

4.1.1.5. Severity of Impact

Severity of impact is assessed from the grading of Degree of Impact and Importance of the environmental factor using the matrix in Table 4.4. If it is not possible to grade Degree of Impact and/or Importance, an assessment is given based on expert judg-ment.

HR3-TR-042 v7 56 / 125 Table 4.4 The matrix used for the assessment of the Severity of Impact.

Importance of the environmental component

Very high High Medium Low

Table 4.5 shows the explanation for each grade of the Severity of Impact. Based on the Severity of Impact, such an expert judgement can state the significance of the impact through the provided phrases. The contents of the table have been defined by Energinet.dk.

Table 4.5 The definition of Impact to an environmental factor. The column to the left is an attempt to include the overall assessment methodology to the scheme defined by Energinet.dk.

Impacts are large in extent and/or duration.

Re-occurrence or likelihood is high, and irre-versible impacts are possible.

(Der forekommer påvirkninger, som har et stort omfang og/eller langvarig karakter, er hyppigt fore-kommende eller sandsynlige, og der vil være mu-lighed for irreversible skader i betydelig omfang).

High Moderate nega-tive impact

(Moderat negativ påvirkning)

Impacts occur, which are either relative large in extent or are long term in nature (lifetime of the project). The occurrence is recurring, or the likelihood for recurrence is relatively high.

Irreversible impact may occur, but will be strictly local, on e.g. cultural or natural con-servation heritage.

(Der forekommer påvirkninger, som enten har et relativt stort omfang eller langvarig karakter (f.eks.

i hele anlæggets levetid), sker med tilbagevenden-de hyppighed eller er relativt sandsynlige og måske kan give visse irreversible men helt lokale skader på eksempelvis bevaringsværdige kultur- eller na-turelementer).

Medium Minor negative Impact

Impacts occur, which may have a certain ex-tent or complexity. Duration is longer than

HR3-TR-042 v7 57 / 125

short term. There is some likelihood of an oc-currence but a high likelihood that the impacts are reversible.

(Der forekommer påvirkninger, som kan have et vist omfang eller kompleksitet, en vis varighed ud-over helt kortvarige effekter, og som har en vis sandsynlighed for at indtræde, men med stor sand-synlighed ikke medfører irreversible skader).

Low Negligible nega-tive impact

(Ubetydelig nega-tiv påvirkning)

Small impacts occur, which are only local, uncomplicated, short term or without long term effects and without irreversible effects (Der forekommer små påvirkninger, som er lokalt afgrænsede, ukomplicerede, kortvarige eller uden langtidseffekt og helt uden irreversible effekter).

Low Neutral / no impact (Neutral/uden påvirkning)

No impact compared to status quo

(Ingen påvirkning i forhold til status quo).

Positive impacts

(Positive påvirkninger)

Positive impact occurring in one or more of the above statements

(Der forekommer positive påvirkninger på en eller flere ovennævnte punkter).

4.1.1.6. Significance

The impact assessment is finalised with an overall assessment stating the significance of the predicted impacts. This assessment of significance is based on expert judge-ment. The reasoning for the conclusion on the significance is explained. Aspects such as Degree and Severity of Impact, recovery time and the Importance of the environ-mental factor are taken into consideration.

4.1.1.7. Assessment of cumulative impacts

The aim of the assessment of cumulative impacts is to evaluate the extent of the envi-ronmental impact of the project in terms of intensity and geographic extent compared with other projects in the area and the vulnerability of the area. The assessment of the cumulative conditions includes activities associated with existing utilised and unutilised permits or approved plans for projects.

HR3-TR-042 v7 58 / 125 When more projects within the same region affect the same environmental conditions at the same time, they are defined to have cumulative impacts. A project is relevant to include, if the project meets one or more of the following requirements:

 The project and its impacts are within the same geographical area as the Pro-ject

 The project affects some of the same or related environmental conditions as the Project

 The project has permanent impacts in its operation phase interfering with im-pacts from the Project

For each environmental component it is considered if cumulative impact with the pro-jects above is relevant.

4.1.1.8. Assessment of transboundary pressures

According to the Espoo Convention on Environmental Impact Assessment in a Trans-boundary Context and EU Directive 85/337/EEC the offshore wind farm Horns Rev 3 can potentially implement transboundary environmental impacts.

The Espoo Convention’s primary aim is to prevent, mitigate and monitor environmental damage by ensuring that explicit consideration is given to transboundary environmen-tal factors before a final national decision is made as to whether to approve a project.

In addition, the objective of the Espoo Convention is the identification and communica-tion of potential transboundary impacts to stakeholders via the applicacommunica-tion of an im-pact assessment.

The assessment of the transboundary pressure in connection with migratory birds will be followed according to a verbal argumentative assessment based upon expert judg-ment.

4.1.1.9. Impacts related to climate change

On the basis that the currently expected lifetime of the offshore wind farm Horns Rev 3 is estimated to about 25 years, we do not expect any impacts associated with cli-mate change. Thus, this aspect is not discussed further in this report.

4.1.1.10. Mitigation and compensation issues

A significant part of the purpose of an EIA is to optimize the environmental aspects of the project applied for, within the legal, technical and economic framework.

Remediation measures are described in the technical background reports. The most important ones are included in the EIA.

HR3-TR-042 v7 59 / 125 4.1.2 Application of the Assessment methodology for migratory birds

4.1.2.1. Magnitude of pressure

According to the assessment methodology (see Horns Rev 3-TM-017 Assessment methodology), the magnitude of a pressure is classed “very high” in case recovery takes longer than 10 years or is permanent and its range is “international”. At the individual level, collisions with wind turbines (permanent structures) are assumed to be lethal (irreversible) in almost all cases, but the risk of such events varies strongly depending on species-specific responsiveness and ecological context. The decommis-sioning of the Horns Rev 3 wind farm is planned to start after about 25 years (see technical description). Until then, the magnitude of pressure for individual migratory birds is theoretically “very high”. With regard to avian collision risk, however, the magnitude of pressure and sensitivity cannot be assessed independently. At the popu-lation level, the magnitude of pressure (collision rate) depends on species-specific behaviour (e.g. flight height, avoidance rate), which determines a species’ sensitivity (see below). We therefore assume that for the risk of collision, the magnitude of the pressure is proportional to the degree of species’ sensitivity. In the case of potential barrier effects imposed on migrating birds, the magnitude of pressure can be consid-ered to be generally “low”, as the hypothetical adverse effect, i.e. higher energy ex-penditure due to detours, is temporary and unlikely to result in significant drawbacks for species that travel at intercontinental spatial scales.

4.1.2.2. Sensitivity

To assess the sensitivity of migratory birds concerning the risk of collision and barrier effects, several species-specific aspects, such as density (in staging/foraging water birds), migration/flight rate, flight altitude, sensory capacities determining avoidance behaviour, have to be taken into account. The sensitivity of a certain species or spe-cies group towards a given pressure can be ranked according to evidence-based knowledge and/or on the basis of output values resulting from collision risk models (e.g. Band 2012). The latter modelling approach can only by performed if adequate input data (density values) are available. For some migratory birds over Horns Rev (individuals and species that fly by night and remain unnoticed), adequate site-specific information is generally scarce, because acoustical ground-truthing of radar infor-mation is limited to those birds that call by night. The sensitivity analysis provided for the Horns Rev 3 project was therefore based predominantly on evidence from post-construction surveys carried out elsewhere, on literature-based meta-analyses (Fur-ness et al. 2013) and on basic ornithological knowledge. In cases where species-specific information on migration intensity was scarce (small-bodied passerines, pi-geons, waders), qualitative sensitivity statements were performed for each relevant species group (or ecotype), and conclusions were generalized across taxa. For the relevant water and seabird species documented in the area around Horns Rev 3, model predictions of the risk of collision were assessed quantitatively, introducing site-specific survey data into the revised version of the Band model (Band 2012). As mentioned above, the magnitude of pressures arising from collisions and from barrier effects can-not be unequivocally separated from the degree of species-specific sensitivity

esti-HR3-TR-042 v7 60 / 125 mates. Furthermore, there is a strong negative dependence between the risk of colli-sion and the strength of the barrier effect, such that when the barrier effect is com-plete (i.e., macro-avoidance rate is 100%), the risk of collision can be formally set to zero.

4.1.2.3. Degree of impact

In order to determine the degree of impact, the magnitude of pressure and the indices of sensitivity are formally combined in a matrix (see table 4.6), resulting in species-specific scores of the degree of impact. As mentioned above, the magnitude of pres-sure and the sensitivity of a species or species group are considered in conjunction when assessing the risk of collision and barriers to movement. Consequently, the de-gree of impact equals both input ratings, or in other words, for a bird species that is prone to collide due to its flight behaviour and sensory ecology (sensitivity classed

“very high”) the magnitude of pressure and the degree of impact is predicted to be

“very high”, too.

Table 4.6 Criteria for assessing the Degree of Impact for migrating birds in the Horns Rev 3 area based on the sensitivity of a species to a pressure.

Construction-, struc-ture- or operation related pressures of

the project

Degree of

Im-pact Description of the Degree of Impact

Barrier effect

Very high Barrier is complete for a large pro-portion of a migratory population.

There are no alternative flight routes. No connectivity between areas at different sides of the barri-er.

High Barrier results in strong behavioural reactions of flying birds. Reduced connectivity between areas at dif-ferent sides of the barrier.

Medium Barrier results in reactions, but will be crossed eventually by flying birds.

Minor Minor barrier effect; birds show minor reactions and fly above or between the structures.

Collision risk

Very high A high proportion of a migratory population in the area is expected to collide with the structure on a regu-lar basis under a wide range of con-dition concon-ditions.

High A small proportion of birds flying in the area are expected to collide with the structure on a regular basis.

Adverse weather conditions are expected to increase collision rates.

Medium Collisions are unlikely, but adverse weather conditions may result in

HR3-TR-042 v7 61 / 125

Description of the Degree of Impact

collision incidents.

Minor Collisions are unlikely. Only single birds are expected to collide with the structure.

Band Model

For calculating the collision risks for migrating sea birds, we used the modified version of the collision model issued by Band (2012). We included those bird species relevant to the Horns Rev area, following Skov et al. 2012 (i.e., Red-/Black-throated Diver;

Northern Gannet; Common Scoter; small gull species, including Common Gull, Black-headed Gull, Little Gull; large gull species, including Herring Gull, Great- and Lesser Black-backed Gull; Kittiwake; terns, including Sandwich Tern, Common Tern and Artic Tern) and which were documented during aerial bird surveys on-site, which has been the general practice in previous EIA in the Horns Rev area. A detailed description of the model has been published by Band (2012). In the following, we specify the input data introduced into the model.

Bird length (m) and wingspan (m) were represented by mean values derived from Svensson et al. (1999). Values of species-specific flight speeds (m/s) were taken from the meta-analysis by Alerstam et al. (2007), except for the average flight speed of the Northern Gannet, which was derived from data published by Pennycuick (1987). Noc-turnal activity factors - 1 (hardly any flight activity at night) to 5 (much flight activity at night) - have been applied by data of Garthe and Hüppop (2004), as well as King et al. (2009) for most of the modelled species. The nocturnal activity factor for the Com-mon Scoter was down-scaled from 3 to 1, following Skov et al. (2012), assuming that night-activity levels are comparatively low in this species (cf., Guillemette et al. 2007;

Lewis et al. 2005).

Site-specific bird densities were based on nine flight surveys carried out in the Horns Rev 3 study area from January 2013 to September 2013 (see report on resting birds for Horns Rev 3 (Dorsch et al. 2013) In the majority of cases, the relative proportion of birds in flight was based on published monitoring information as described in Skov et al. (2012). For example, about 2% of all staging divers counted in this area spend the time aloft, 64% of all counted Northern Gannets and 43% of all large gulls are on the wing (Skov et al. 2012). The proportion of time a bird spent at rotor height was

Site-specific bird densities were based on nine flight surveys carried out in the Horns Rev 3 study area from January 2013 to September 2013 (see report on resting birds for Horns Rev 3 (Dorsch et al. 2013) In the majority of cases, the relative proportion of birds in flight was based on published monitoring information as described in Skov et al. (2012). For example, about 2% of all staging divers counted in this area spend the time aloft, 64% of all counted Northern Gannets and 43% of all large gulls are on the wing (Skov et al. 2012). The proportion of time a bird spent at rotor height was

In document Horns Rev 3 Offshore Wind Farm Technical report no. 8 (Sider 52-0)